Mount for a boat propulsion unit

ABSTRACT

A mount for a boat propulsion unit comprises a collar for mounting around an aperture in a boat&#39;s hull, the collar having an annular groove on an inner surface thereof; a first mating part for mounting an inboard portion of a propulsion unit to the boat; and a second mating part, connectable to the first mating part, for mounting an outboard portion of a propulsion unit to the boat. The first and second mating parts are connectable through the collar and are configured such that when they are connected they form an external annular recess in an outer surface and an annular gasket is located partly in the groove and partly in the recess to form a seal there-between.

FIELD OF THE INVENTION

This invention relates to a mount for a boat propulsion unit.Particularly, but not exclusively, the invention relates to a mount formounting an inboard propulsion unit in a boat hull.

BACKGROUND TO THE INVENTION

Aspects of the present invention are particularly concerned with themounting of electric propulsion units that consist of a saildriveprojecting from the bottom of a boat's hull and that have an inboardmotor mounted above the saildrive. In essence, a saildrive can beconsidered as a sailboat's equivalent of a motorboat's sterndrive, whichprojects from the stern of a boat and usually has a drive mountedoutside of the hull (and is therefore also known as an outdrive). Asaildrive is significantly different to a traditional inboard motorsince it is not connected to the motor via a standard propeller shaft.Instead, inside a saildrive casing there is normally an L-gear thatconsists of a vertical (pinion) shaft, a horizontal (propeller) shaftand a bevel gear. A compact electric motor can then be positioned abovethe saildrive with the motor drive shaft extending downwardly throughthe hull to create a very compact unit maximizing the space in insidethe boat.

An electric propulsion unit, such as that described above incorporatinga saildrive, is normally rigidly mounted to the bottom of a boat eitherdirectly to the hull or onto a motor bed. Such a rigid mounting isfairly easy to achieve, however, a disadvantage is that a rigid mountingwill transfer any vibrations caused by the propeller directly to thestructures of the boat. This may result in noise, vibrations and, in theworst case, damage to some structures. It will also be understood thatit is necessary to seal the gap between the drive/propulsion unit andthe hull to prevent water ingress.

U.S. Pat. No. 7,690,959 discloses a mount suitable for a very largeinboard drive unit. A simplified illustration of this arrangement isprovided in FIG. 1 which shows a cross-section through one side of themount 10. A first mounting plate 12 is provided on an upper portion ofthe boat drive unit and has an upwardly facing frustoconical mountingsurface 14. A second mounting plate 16 is provided within the hull andhas a downwardly facing frustoconical mounting surface 18. A mountingcollar 20 is provided in the boat hull and includes a peripheral flange22 extending inwardly of the collar and having a first frustoconicalmounting surface 24 facing upwardly and second frustoconical mountingsurface 26 facing downwardly. Two compressible rings 28 are providedbetween the mounting surfaces 24, 26 of the collar 20 and the respectivemounting surfaces 14, 18 of the first and second mounting plates 12, 16.Thus, it can be seen that, in use, each of the rings 28 will becompressed between opposed parallel surfaces such that each ring 28 willbe subjected to forces applied substantially through its centre (i.e.from a contact point at one side of the ring 28 to a contact point atthe diametrically opposite side of the ring 28). In other words, thefirst and second mounting plates 12, 16 in this arrangement provide acompressive force directly through each ring 28 to the collar 20 to sealthe gap there-between.

European patent application No. EP 0,811,511 discloses another mountingsystem for use with a sterndrive propulsion unit and which employs avery similar sealing arrangement to that described above.

It is an aim of the present invention to provide an alternative mountfor a boat propulsion unit.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amount for a boat propulsion unit comprising:

-   -   a collar for mounting around an aperture in a boat's hull, the        collar having an annular groove on an inner surface thereof;    -   a first mating part for mounting an inboard portion of a        propulsion unit to the boat;    -   a second mating part, connectable to the first mating part, for        mounting an outboard portion of a propulsion unit to the boat;    -   the first and second mating parts being connectable through the        collar and being configured such that when they are connected        they form an external annular recess in an outer surface; and    -   an annular gasket locatable partly in said groove and partly in        said recess to form a seal there-between.

Embodiments of the invention effectively provide a flexible mountingarrangement in which the traditionally separate elements required forfixing two parts together and sealing the space between them is combinedin a single component by way of the gasket of the present invention.Thus, the gasket serves to provide a watertight seal between the collarand the first and second parts; acts as a flexible (“floating”) mountingfor the propulsion unit in the boat's hull; and also serves to transferthe power generated by the propulsion unit to the boat. An advantage ofthe present invention is that the gasket can absorb (or at least dampen)vibrations and thereby prevent (or minimise) the transfer of suchvibrations from the propulsion unit to the boat since there is no rigidfixing or hard contact between the boat and the propulsion unit. Themount requires only a few discrete components and has a simpleconstruction making it quick and easy to install. There is also no needfor any electrical connections between the boat and the propulsion unit.Furthermore, the mount can be made to be compact and light and yetstrong.

In use, the first and second mating parts may be configured to apply aforce to compress the gasket when the first and second mating parts areconnected. The force may be applied generally vertically through aportion of the gasket received in the recess. Thus, the force tocompress the gasket may be transmitted through the innermost side of thegasket causing the gasket to expand radially outwardly into the grooveto seal against the collar.

The applicants have found that the shape of the groove in the collar andthe shape of the recess formed by the first and second mating parts caninfluence the power transfer and vibration dampening properties of themount. Accordingly, the shapes of the groove and recess should becareful chosen to provide the desired properties.

The groove and the recess may have similar or different cross-sections.

The groove and/or the recess may be generally V-shaped or C-shaped.Thus, the groove and/or the recess may be formed by two inclined annularsurfaces having an angle of less than 180 degrees there-between. Theangle may be between 180 degrees and 90 degrees but is preferably 90degrees or less. The inclined surfaces may join via a curved interfaceor a straight (e.g. vertical) interface. In certain embodiments, thegroove and/or recess may be part-circular, for example, hemispherical.

The gasket may comprise rubber and may be in form of an O-ring. Asabove, the type of rubber employed in the gasket may influence the powertransfer and vibration dampening properties of the mount.

The gasket may be substantially toroidal forming a circle in plan view.Alternatively, the gasket may be substantially oval, obround orelongated in plan view. The use of an oval, obround or elongated gasketmay be particularly advantageous since it has been found thatapproximately 80% of the forces applied to the gasket in use are likelyto be in the forwards and backwards directions and these can be mosteffectively managed by having a gasket elongated in the forwards andbackwards directions.

It will be understood that the plan view shape of the groove and therecess will be required to correspond to the shape of the gasket so thatthe gasket can be partly received in the groove and the recess, when inuse. Although not strictly necessary, the shapes of the collar and/orthe first and second mating parts may also generally correspond to theshape of the gasket in plan view.

The gasket may have a vertical cross-section that is substantiallycircular. However, other cross-sections may be employed to impartspecific characteristics to the gasket (e.g. to influence thecompression characteristics and/or the load transfer characteristics ofthe gasket).

The collar may be substantially cylindrical or may be constituted by asubstantially oval, obround or elongate section of tubing. As above, theapplicants have found that the shape and size of the collar can affectthe power transfer and vibration dampening properties of the mount andso these should also be carefully chosen to provide the desired results.

The collar may be affixed in a hole in the boat's hull or it may beintegrally formed with the hull (e.g. by moulding the hull including thecollar from glass reinforced plastic). Alternatively, the collar may belaminated in the boats hull. Where the collar is a discrete componentfor affixing to the hull, it may be formed from glass reinforcedplastic, steel, aluminium or other durable materials.

The first and second mating parts may be made of metal and may beconfigured to form a continuous channel there-through.

The first mating part may be provided on a motor and the second matingpart may be provided on a propeller unit such as a saildrive.

The first and second mating parts may be connectable via an attachmentmechanism which may comprise complementary inter-engaging parts and maybe configured for screwing the first and second parts together.Alternatively, the attachment mechanism may be constituted by abayonet-type or other mechanical fastening.

The propulsion unit may be in the form of an inboard propulsion unit, anoutboard propulsion unit, an electric propulsion unit, an internalcombustion propulsion unit, a saildrive propulsion unit or a so-calledpropulsion pod unit.

According to a second aspect of the present invention there is provideda boat propulsion unit comprising a mount according to the first aspectof the present invention.

According to a third aspect of the present invention there is provided aboat comprising a mount according to the first aspect of the presentinvention.

According to a fourth aspect of the present invention there is provideda method of mounting a propulsion unit on a boat comprising:

-   -   providing a collar around an aperture in a hull of the boat, the        collar having an annular groove on an inner surface thereof;    -   locating an annular gasket in the collar so that the gasket        partly resides in said groove;    -   providing a first mating part on an inboard portion of a        propulsion unit and a second mating part, connectable to the        first mating part, on an outboard portion of a propulsion unit;        and    -   connecting the first and second mating parts through the collar        so that the first and second mating parts form an external        annular recess in which said gasket is partly located.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention will now be described indetail with reference to the accompanying drawings, in which:

FIG. 1 shows a cross-sectional view of one side of a prior art mountingarrangement for a boat propulsion unit;

FIG. 2A shows an exploded view of a mount according to a firstembodiment of the present invention;

FIG. 2B shows a part cross-sectional view of an assembled mount, similarto that shown in FIG. 2A, when attached to an inboard motor andsaildrive of a boat according to a second embodiment of the presentinvention;

FIG. 3 shows a part cross-sectional view of a mount similar to thatshown in FIG. 2A when assembled;

FIG. 4 shows an enlarged cross-sectional view of a portion of the mountof FIG. 2B showing that the gasket is located in a groove having facesangled 90 degrees apart;

FIG. 5 shows an enlarged cross-sectional view of a portion of a mountaccording to a third embodiment of the present invention, wherein agasket is located in a groove having faces angled 75 degrees apart;

FIG. 6 shows an enlarged cross-sectional view of a portion of a mountaccording to a fourth embodiment of the present invention, wherein agasket is located in a groove having hemispherical faces;

FIG. 7A shows an enlarged cross-sectional view of the mount of FIG. 2B,showing an attachment mechanism prior to assembly of the mount; and

FIG. 7B shows a view similar to that shown in FIG. 7A after theattachment mechanism has been employed to assemble the mount.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

With reference to FIG. 2A, there is illustrated a mount 30 for a boatpropulsion unit (not shown) according to a first embodiment of thepresent invention. The mount 30 comprises a hollow generally cylindricalcollar 32 (also known as a motor bed). In this embodiment, the collar 32is designed to be integrally moulded within a hole in the bottom of aboat's hull (not shown). The collar 32 includes an inner annular groove34 configured to partly receive an annular rubber gasket in the form ofO-ring 36. In this particular embodiment, the collar 32 also includes anannular bulge 37 on its external surface, to accommodate the innerannular groove 34.

It will be noted from FIG. 2A that the mount 30 has a generally obroundshape when viewed from above. As stated previously, this shape isadvantageous in handling the forwards and backwards forces applied tothe mount 30 when in use.

The mount 30 further comprises an upper part 38 configured forattachment to an inboard motor or its housing (not shown) and a lowerpart 40 configured for attachment to a saildrive unit (not shown).Although not shown in the Figures, the upper part 38 and the lower part40 will be hollow in practice to allow a motor drive shaft to extendthrough the mount 30 to operate the saildrive. The upper and lower parts38, 40 also include an attachment mechanism (not shown) which isdescribed below in relation to FIGS. 7A and 7B.

In use, the upper and lower parts 38, 40 are attached together byinserting the upper part 38 into the collar 32 from within the boat andinserting the lower part 40 into the collar 32 from below the boat. Theparts 38, 40 are shaped in such way that they will form a recess intowhich the gasket 36 will be partly located so that the parts 38, 40 canapply pressure on the gasket 36 when they are engaged and tightenedtogether. This constant pressure (pre-stress) will serve to provide awatertight seal between the hull and the propulsion unit as well asproviding a flexible mounting for the unit. It will be understood that asuitable pressure will required in order keep the mount 30 properlysealed also when thrust is applied to the boat.

In this particular embodiment, the upper part 38 has a downwardlyextending frustoconical surface 42 terminating in a short cylindricalsurface 44. The lower part 40 has an upwardly extending frustoconicalsurface 46 also terminating in a short cylindrical surface 48. Thefrustoconical surfaces 42, 46 are inclined such that they form an anglethere-between of approximately 90 degrees when the upper and lower parts38, 40 are engaged.

The applicants have determined several ways to adjust the vibrationdampening and sealing properties of the mount 30. More specifically,they have discovered that by increasing the size of the collar 32 andparts 38, 40 the mount 30 can be configured to suit larger or morepowerful propulsion units. In addition, the shape of the collar 32 canbe changed depending on the nature of the drive to be used. A fixeddrive is thought to benefit from an oval shaped mounting (as per FIG.2A) while a round collar 32 is believed to be suitable for a rotatingdrive or pod-type propulsion unit.

The shape of the groove 34 in the collar 32, the shape of the recessformed by the parts 38, 40, the tightness of the engagement between theparts 38, 40 as well as the size of the gap between the collar 32 andparts 38, 40 are all considered to affect the “hardness” (orflexibility) of the mount 30. The more free space the gasket 36 has todeform into, the softer the mounting will be. A powerful unit mayrequire a relatively hard mounting to keep movement of the propulsionunit to an acceptable level. By carefully choosing a combination ofthese properties a suitable level of vibration dampening can beachieved.

FIG. 2B shows a part cross-sectional view of an assembled mount 50,similar to that shown in FIG. 2A, when attached to a propulsion unitcomprising an inboard motor 52 and saildrive 54 of a boat 56, accordingto a second embodiment of the present invention. The mount 50 comprisesa hollow obround cylindrical collar 58 affixed within a hole in thebottom of the boat's hull 56. The collar 58 includes an inner annularV-shaped groove 60 configured to partly receive an annular rubber gasketin the form of O-ring 62.

As above, the mount 50 further comprises an upper part 64 which, in thiscase, is attached to the inboard motor 52 and a lower part 66 which, inthis case, is attached to the saildrive 54. Also as described above, theupper part 64 and the lower part 66 will be hollow in practice to allowa motor drive shaft (not shown) to extend through the mount 50 tooperate the saildrive 54 and the upper and lower parts 64, 66 alsoinclude an attachment mechanism (not shown) which is described below inrelation to FIGS. 7A and 7B. The upper part 66 has a downwardlyextending frustoconical surface 70 which mates with an upwardlyextending frustoconical surface 72 of the lower part 66 to form a recess74 in which the O-ring 62 is partly engaged. As above, the frustoconicalsurfaces 70, 72 are inclined such that they form an angle there-betweenof approximately 90 degrees when the upper and lower parts 64, 66 areengaged.

FIG. 3 shows a part cross-sectional view of a mount 80, similar to thatshown in FIG. 2A, when assembled. The mount 80 is identical to thatshown in FIG. 2A except that the mount 80 includes a collar 82 which hasa thicker wall than the collar 32 and, as such, no external bulge isrequired in the collar 82 in order to provide for the annular groove 34.

FIG. 4 shows an enlarged cross-sectional view of a portion of the mount50 of FIG. 2B showing the gasket 62 located in the groove 60, which isformed by inclined surfaces 90, 92 angled 90 degrees apart. As describedabove, the frustoconical surfaces 70, 72 of the upper and lower parts64, 66 in this embodiment are inclined such that they form an angle of90 degrees there-between when the upper and lower parts 64, 66 areengaged.

Although it is not evident from FIG. 4, it will be understood that whenthe first and second parts 64, 66 are attached to each other they willform a compressive force substantially vertically through the portion ofthe gasket 62 trapped there-between. This will cause the gasket 62 tobulge in a substantially outwardly direction so as to form a tightsealing fit within the groove 60.

FIGS. 5 and 6 show alternative shapes of grooves and recesses that maybe employed in embodiments of the present invention. In each case, onlyone side portion of the mount is shown to illustrate the shapes of thegrooves and recesses. In each case, the remainder of the mount isidentical to that shown in FIG. 2B and so like reference numerals willbe employed where appropriate.

FIG. 5 shows a mount 100, similar to that of FIG. 4 but wherein theinclined surfaces 90′, 92′ of the groove 60′ are angled 75 degrees apartand the frustoconical surfaces 70′, 72′ (forming the recess 74′) arealso angled 75 degrees apart. Power vectors are also illustrated in FIG.5 to show that the forces applied by the upper and lower parts 64′, 66′in this embodiment are again directed generally vertically through theinnermost side of the gasket 62.

FIG. 6 shows a further mount 110 wherein the groove 60″ and the recess74″ each have respective hemispherical surfaces 112, 114 facing towardseach other and enclosing the gasket 62 there-between. As per previousfigures, for ease of clarity, the gasket 62 is not shown in acompression. It will, however, be understood that in use, the attachmentof the first and second parts will exert a compressive force on thegasket 62 to ensure that it forms a sealing relationship with thecollar.

FIGS. 7A and 7B show enlarged cross-sectional views of the mount 50 ofFIG. 2B, before and after the first and second parts 64, 66 areattached. In this case an attachment mechanism is provided whichcomprises two screws 120 which are arranged to pass upwardly throughrespective holes 122 in the second part 66 to screw into complementaryscrew-threaded apertures 124 in the first part 64. In other embodiments,screws may be provided through the first part 64 into the second part66.

As shown in FIG. 7B, when the screws 120 are tightened to secure thefirst and second parts 64, 66 together, the gasket 62 is compressedwithin the recess 74 and groove 60 both to seal the mount 50 and totransfer load from the propulsion unit to the boat hull.

Using an O-ring for attaching the propulsion unit to the boat hull isconvenient as this kind of mechanical gasket is readily available as astandard part and will thus keep costs down. It is noted that O-ringsare normally used only for sealing in either static or dynamicmechanical applications. However, in the present invention the O-ring isemployed in a different way since (in addition to sealing the mounting)it will be the component that insures that the whole propulsion unit issecured to the boat as well as helping to dampen any vibrations.

It will be appreciated by persons skilled in the art that variousmodifications may be made to the above embodiments without departingfrom the scope of the present invention.

1. A mount for a boat propulsion unit comprising: a collar for mountingaround an aperture in a boat's hull, the collar having an annular grooveon an inner surface thereof; a first mating part for mounting an inboardportion of a propulsion unit to the boat; a second mating part,connectable to the first mating part, for mounting an outboard portionof a propulsion unit to the boat; the first and second mating partsbeing connectable through the collar and being configured such that whenthey are connected they form an external annular recess in an outersurface; and an annular gasket locatable partly in said groove andpartly in said recess to form a seal there-between.
 2. The mountaccording to claim 1 wherein the first and second mating parts areconfigured to apply a force to compress the gasket when the first andsecond mating parts are connected.
 3. The mount according to claim 1wherein the first and second mating parts are configured to apply aforce to compress the gasket when the first and second mating parts areconnected, and wherein the force is applied generally vertically througha portion of the gasket received in the recess.
 4. The mount accordingto claim 1 wherein the first and second mating parts are configured toapply a force to compress the gasket when the first and second matingparts are connected, and wherein the force is applied through theinnermost side of the gasket causing the gasket to expand radiallyoutwardly into the groove to seal against the collar.
 5. The mountaccording to claim 1 wherein the groove and the recess have similarcross-sections.
 6. The mount according to claim 1 wherein the grooveand/or the recess is generally V-shaped or C-shaped.
 7. The mountaccording to claim 1 wherein the groove and/or the recess is formed bytwo inclined annular surfaces having an angle of less than 180 degreesthere-between.
 8. The mount according to claim 1 wherein the grooveand/or the recess is formed by two inclined annular surfaces having anangle of less than 90 degrees there-between.
 9. The mount according toclaim 1 wherein the groove and/or the recess is formed by two inclinedannular surfaces having an angle of less than 180 degrees there-between,and wherein the inclined surfaces join via a curved or a straightinterface.
 10. The mount according to claim 1 wherein the groove and/orrecess is generally V-shaped or C-shaped, and wherein the groove and/orrecess is part-circular.
 11. The mount according to claim 1 wherein thegasket is circular, oval, obround or elongated in plan view.
 12. Themount according to claim 1 wherein the collar is substantiallycylindrical or constituted by a substantially oval, obround or elongatesection of tubing.
 13. The mount according to claim 1 wherein the collaris integrally formed in a boat's hull.
 14. The mount according to claim1 wherein the first mating part is provided on a motor and the secondmating part is provided on a propeller unit.
 15. The mount according toclaim 1 wherein the first and second mating parts are connectable via anattachment mechanism.
 16. The mount according to claim 1 wherein thefirst and second mating parts are connectable via an attachmentmechanism, and wherein the attachment mechanism comprises complementaryinter-engaging parts, or is configured for screwing the first and secondparts together or is constituted by a bayonet-type fastening.
 17. Themount according to claim 1 configured for mounting a propulsion unit inthe form of an inboard propulsion unit, an outboard propulsion unit, anelectric propulsion unit, an internal combustion propulsion unit, asaildrive propulsion unit or a propulsion pod unit.
 18. The mountaccording to claim 1, the first and second mating parts being configuredsuch that, when connected, they are able to accommodate a motor driveshaft passing axially through the mount.
 19. A boat propulsion unitcomprising a mount according to claim
 1. 20. A boat comprising a mountaccording to claim
 1. 21. A method of mounting a propulsion unit on aboat comprising: providing a collar around an aperture in a hull of theboat, the collar having an annular groove on an inner surface thereof;locating an annular gasket in the collar so that the gasket partlyresides in said groove; providing a first mating part on an inboardportion of a propulsion unit and a second mating part, connectable tothe first mating part, on an outboard portion of a propulsion unit; andconnecting the first and second mating parts through the collar so thatthe first and second mating parts form an external annular recess inwhich said gasket is partly located.